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Climate Hustle

16  ^  more years of global warming

Posted on 10 January 2013 by Kevin C

Update 21/02/2013: Troy Masters is doing some interesting analysis on the methods employed here and by Foster and Rahmstorf. On the basis of his results and my latest analysis I now think that the uncertainties presented here are significantly underestimated, and that the attribution of short term temperature trends is far from settled. There remains a lot of interesting work to be done on this subject.

Human greenhouse gas emissions have continued to warm the planet over the past 16 years. However, a persistent myth has emerged in the mainstream media challenging this.  Denial of this fact may have been the favorite climate contrarian myth of 2012, first invented by David Rose at The Mail on Sunday with an assist from Georgia Tech's Judith Curry, both of whom later doubled-down on the myth after we debunked it.  Despite these repeated debunkings, the myth spread throughout the media in various opinion editorials and stunts throughout 2012. The latest incarnations include this article at the Daily Mail, and a misleadingly headlined piece at the Telegraph.

As a simple illustration of where the myth goes wrong, the following video clarifies how the interplay of natural and human factors have affected the short-term temperature trends, and demonstrates that underneath the short-term noise, the long-term human-caused global warming trend remains as strong as ever.

In particular, once the short-term warming and cooling influences of volcanic eruptions, solar activity, and El Niño and La Niña events are statistically removed from the temperature record, there is no evidence of a change in the rate of greenhouse warming. This replicates the result of a study by Foster and Rahmstorf (2011) under slightly different assumptions.

The human contribution to global warming over the last 16 years is essentially the same as during the prior 16 years¹. Human-caused greenhouse warming, while partially hidden by natural variations, has continued in line with model projections². Unless greenhouse gas emissions are brought under control, we will see faster warming in the future³.


  • The 16-year temperature trend provides no evidence to suggest that the consensus understanding of human-caused climate change is incorrect.

Further Reading:

For details of the method, see the Advanced rebuttal to the myth 'no warming in 16 years'.

The results of this analysis are consistent with a statement by WMO Secretary-General Michel Jarraud:

"Naturally occurring climate variability due to phenomena such as El Niño and La Niña impact on temperatures and precipitation on a seasonal to annual scale. But they do not alter the underlying long-term trend of rising temperatures due to climate change as a result of human activities"

Credits: Video: Kevin C. Voiceover: Daniel Bailey. Advice: The SkS team.
Teaser graphics: What happened next? Does this look like global warming?

We have attempted to keep the language in this video at the same non-technical level as the media stories it refutes. As a result, it has been necessary to simplify much of the terminology. The following notes are for technically literate readers.
¹ i.e. If a change in gradient is allowed at 1997 then the change in gradient is not statistically significant (even at the 1σ level).
² i.e. Within the envelope of AR4 trend projections.
³ On the basis of both AR4 projections and that global GHG emissions are increasing.

Update 21/02/2013: Troy Masters is doing some interesting analysis on the methods employed here and by Foster and Rahmstorf. On the basis of his results and my latest analysis I now think that the uncertainties presented here are significantly underestimated, and that the attribution of short term temperature trends is far from settled. There remains a lot of interesting work to be done on this subject.

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Comments 51 to 100 out of 139:

  1. Thanks Rob. And I certainly understand why the comments were blocked. I think the moderation had created a tone that was far better than the other videos on climate change. But I can only imagine it was a nightmare. Chris Mooney is likely correct and it is very difficult to maintain a calm, rational tone on a forum like YouTube, although you do it better than most. The only thing I wondered was if the number of comments might play a role in how highly YouTube recommends videos to those looking at similar stuff. However it looks like the number of views continues to climb.
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  2. I was quite enjoying the comments bunfight on the Youtube version. Rob Honeycutt was answering every silly comment with real science and I was chipping in with my down-home analogies to try to get through to the worst of them the difference between large cyclical variations and small cumulative forcings - waves vs tide on a beach and over-eating averaged over decades vs binge eating/crash diets.

    Most "anything but CO2" commenters seem incapable of understanding why picking start/finish times on a proper graph can give a totally false impression of the underlying trend. Sometimes, simple analogies like those above can get through.
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  3. Yes. Multiple regressions should Always be represented this way! There's probably no program which would do this automatically, so I imagine that has taken quite a while. Excellent. [DB: good job you too]
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  4. Climate warming caused by human activity (CO2) may not be the worst long term problem. Public perception of need to limit CO2 emissions, has lead to demand and acceptance of alternate energy production. Nicely this would mean wind, solar, etc, just these not yet cost efficient enough for a normal person to pay for. Practically this means rebirth of fission. About 63 new fission reactors are currently in construction, and many more projects have been approved (source: internet, reliability: uncertain). Using fission may have much longer lasting ill effects to future life than burning fossil fuels.
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  5. pekka.lehtikoski, I'm in a bit of a blinding rush, so cannot link you to the relevant data, but they are out there, in droves:

    -Thorium reactors are much more safe and reliable than standard 1st/2nd generation NPPs;

    -The amount of radioactivity released from the burning of coal--if that is what you're concerned about--is WAY more, in a cumulative sense than all the radioactivity from all the nuclear accidents combined.

    -I'm no huge fan of even 3rd/4th gen. NPPs but they must be considered, if we insist on being 7+ billion souls.

    Frankly, I personally think it irresponsible to future generations to insist on such, and that to maintain the viability of our species, and the survival of many others, we must do *everything* in our power to address our insatiable need for energy: Not the least of those is conservation.
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  6. I hate to point out the obvious, but at 1:20 when you say "whats left is the human contribution....."
    How do you know what is left is the human contribution.

    To be scientific, it should be:
    1. Remove volcanic activity.
    2. Remove el nina activity
    3. Remove all other forms of natural warming/cooling
    4. Whats left is the human contribution

    You seemed to missed out step #3, and just jumped to the conclusion that what is left is ALL human contribution.
    This isn't following a scientific methodology. You cannot assume something and then say it is fact.
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  7. @eon, so what identifiable forms of natural warming/cooling were not included (provide evidence to suggest it has a non-negligible effect on surface temperatures)?

    In my opinion, given this is a video intended for the general public, rather than a scientific journal, I think it is being a bit pedantic to quibble about the definition of "fact". It is fundamentally impossible to gain certain knowledge from experiment or observation (Hume), so if you really wanted to you could say that nobody could state any facts about causal relationships in climate. However, that would be just silly, so you have to draw a line somewhere and use a bit of common sense.
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  8. @ Dikran. I don't claim to know much on the current state climate change research (its something I'm looking into it), but I do know about correct scientific methodology.

    It really should read "Whats left is the human contribution + the unknown contributions that we have yet to discover". You are parcelling all the unknowns under the banner of "human contributions". I could equally walk through this video and do: and what we are left with is "volcanic contribution", thus parcelling all the unknown stuff under volcanic.

    If you are saying that there is absolutely no unknowns of major influence. We are 100% sure of this - then that is fair enough.

    You should be tackling this from the other end.
    - Estimate/Calculate volcanic (i dont know how but you have done it)
    - Estimate/Calculate el-nino
    - Estimate/Calculate human contributions
    - Take all 3 from the graph, then what you are left is is the unknowns.

    Why isn't that more accurate?

    If you don't think this is important, then consider the ozone/cfc 'scare' of many years ago. Recently, it was admitted that the cfc actually didn't have much effect. Even more recently, it is found that there is emissions from the oceans that have a huge effect on the ozone layer.

    My point is: What seemed 100% certainty back then. Turned out to be absolute hogwash. Similarly, this video's content is a "theory" not a "fact" because it is inconclusive due to some basic level assumptions about we are 100% certain we known everything
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  9. Hi Vrooomie
    Thorium reactors might be a better choice. There has been many low power test reactors, most of which closed before 1990. A couple of thorium reactors are currently operating in India (source: wikipedia, reliability: low).
    Fission reactors being constructed now (and accepted near future ones) are not thorium reactors.
    Yes. Burning carbon will cause carbon-14 emissions, which are radioactive. This releases much more radioactivity to environment than nuclear power plants. Anyhow carbon-14 has a relatively short half-life of 5730 years, thus it is not a long term problem (just for next 30000 years or so).
    I do not see nuclear power plants themselves as a problem. End placement of high level waste is the long term problem, and the uranium mining is short term problem. High level waste will stay radioactive for very long time, and toxic even after that. I do not understand how we could contain it safely for millions of years. Besides I do not have faith that all corporations around the world will handle high level waste in very expensive responsible manner, when it can be simply dumped in ocean, with no cost. Short term problem is uranium mining. In Finland (my birth country) Talvivaara cleaning pool dam broke again for the third time, leaking material to rivers and lakes. Even natural uranium has very low radioactivity, it is still toxic heavy metal.
    If only ITER would succeed and provide fission power. Even fission generates radioactive waste, it is only short lived. We would have to worry about containment only for very short time, like a few thousand year.
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  10. @eon writes "really should read "Whats left is the human contribution + the unknown contributions that we have yet to discover". Yes, technically that is true, but there is little evidence to suggest that the "unknown contribution" is not negligible, and so it isn't worth mentioning in a video aimed at a general audience.

    Of course this particular analysis cannot show that the "unknown contribution" is negligible, but the history of climate research goes back a couple of hundred years, and the gross features of climate are pretty well explained by the factors we do know. All scientific results are subject to the "unknown unknowns" so should that caveat be placed on every scientific statement, or just ones relating to anthropogenic climate change?

    Can you give me a reference to a journal paper that shows CFCs were not responsible for the hole in the ozone layer?
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  11. eon:

    Positing substantial "unknown unknowns" affecting surface temperature trends is usually an exercise in what is nicknamed here climastrology.

    IMO it's a waste of time, especially for communicating science to the general public (such as myself).

    Although off-topic, since it's one of the key planks of your argument, please provide citations to peer-reviewed literature to support your assertions regarding the contribution of CFCs to stratospheric ozone depletion.
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  12. @Dikran. OK - I guess I just don't like "dumbed down" science (working in a scientific field myself). I can understand the requirement for estimations / best-guesses and to a certain level assumptions. But just find it alarming that the 'unknowns' / 'inaccuracies' have been conveniently grouped together with the 'human contributions' as one big catch-all.

    I get the purpose of the video. But unfortunately, dumbed-down quickly becomes 'fact' in a lot of people's head. I would argue that is it neither a fact, a theory or a hypothesis because it is not 'testable'. It is a 'theory' in the more general-speak use rather than the scientific use of the word theory.

    Apologise - I don't have details on the CFC - I try dig out what I read. It wasn't a journal - so I shouldn't say "hogwash". But it cast a lot of doubt on the claim, coupled with more recent discoveries that have been referenced in the news. I was mostly trying to illustrate an example of where this kind of assumption has proved very wrong in hindsight and how it could/can be avoided if we avoid 'dumb science'
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  13. eon, claims not appearing in the primary literature seemingly contradicting the current understanding of science (which is supported by the primary literature) can scarcely be construed as "it cast a lot of doubt on the claim".

    Such thinking is hardly scientific.
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  14. @eon - it isn't "dumbed down", it is just missing a caveat regarding something likely to be of no real importance.

    Sadly many discussions of climate get bogged down in sophomoric discussions about scientific method, usually claiming something is not testable. You have provided nothing to support the idea that the "unknown component" is plausible non-negligible, and until you do, all you are doing is engaging in pedantry.

    The fact that you have strong views on CFCs that are not supported by scientific literature suggest that your adherence to scientific method is somewhat inconsistent!
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  15. eon... What you're perhaps missing is there are fundamental accepted facts like, 1) Humans are releasing vast quantities of CO2 into the atmosphere every year, 2) CO2 is well understood to be the strongest well mixed greenhouse gas, and 3) An enhanced greenhouse effect will act to warm the planet.

    It doesn't follow that you absolutely MUST restate and reprove every aspect of the science for a simple presentation to be valuable.

    Given the overwhelming body of scientific evidence showing that humans are having a dramatic affect on the climate system, this presentation is perfectly reasonable.

    It would also be a mistake to suggest this video is proof of a connection between the rise in surface temperature and human causation. It's not, and it's not presented that way. The lesson of the video is that, the surface temperature record is noisy but if you remove some of the known noise (ENSO and Volcanoes) then you can clearly see the trend of the past 30 years is consistent.
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  16. I also have to object to the term "dumbed down" because I don't think that is what has been done here. This, I believe, is a very sophisticated communication piece. Sometimes making complex issues simple and easy for people to comprehend is the most difficult task a scientist can face.
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  17. eon:

    You appear to be beating a variant of the drum that says "you don't know absolutely everything, so you can't claim to know anything at all". As we never know absolutely everything, but we frequently know enough to accomplish many things, this is a drum that just adds noise, not signal.

    If you are going to rest a case on "unknown factors", don't expect to be taken seriously when known factors explain most of what is happening.

    As for your CFC-ozone dismissal - don't throw out the "hogwash" epithet quite yet. When you find your source that "cast a lot of doubt on the claim" and present it here, I suspect that a scientific analysis will show that your source is the one that's doing the pig-cleaning. That doesn't mean that I won't look at your information with an open mind, but my brain hasn't fallen out yet and there is an awful lot of strong science in the CFC-ozone link that would have to be wrong before you'll convince me.
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    Moderator Response: (Rob P) - talk about ozone is wandering off-topic. The future ozone-depleted world avoided was the subject of a peer-reviewed paper released last year, and also this older paper - discussed at NASA Earth Observatory. Note the total ozone and UV index figures. Dodged a bullet there.

    Find an appropriate thread to discuss it, if you so wish.
  18. eon
    As scientists we sometimes want to, and at times need to be pedantic. In our science and how we interpret it, but not necessarily in how we communicate it. The moment at 1:22 into the video can make some of us feel a bit uneasy. But this is not because there is any reason to think it is wrong. Considering how much is known about climate forcings, invoking the "unknown unknown" is not just unhelpful, especially with respect to communication, it is also mostly wishful thinking, and as such not goal oriented. All those who wish there were some unknown factor that only makes us think CO2 is a problem (recall that the physical effects of CO2 in the atmosphere are fact) are basically akin to drug addicts who blame everything but themselves for their problems. How does that help?
    See Dikran @64.
    Ever asked yourself how likely it is that thousands of scientists have yet to discover a major climate factor after so many decades of research?

    And indeed, your CFC assertion is odd ... so we are indeed looking forward to some source of that claim.
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  19. ok, thanks for responses:

    I'm not going to reply to every individual comment as it will take too long. But I will rather answer the general theme (ignoring ozone as per mods request):-
    "yes there unknowns+accuracy issues, but that a) They are small/irrelevant; b) Everything has unknowns, so you can't bury everything in quicksand if it isn't completely conclusive."

    All i'm saying is that the author of the video has took the temperature readings, then subtracted some known figures, and then bundled the remainder all as "caused by humans".

    If that is true, can I ask what you would expect to see on the graph for the pre-man-made-global-warming era, if you subtracted all of the (Volcano+Solar+El Nina factors) as has be done in the video?

    So we have:
    1) Removal of all rises due to volcanos, solar, el-ninas.
    2) In this era, there would be no human CO2 contributions.
    3) It is said there are NO unknown factors (of significance)

    Since no human contributions, no unknown contributions and all the significant factors have been subtracted/added, then by your arguments, we would see a flat graph (+some noise) ?
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  20. @eon, perhaps I ought to get out my time machine and collect some observations so that we can perform the exercise you suggest?

    If you want to know what to expect, then look at some control runs from GCMs. GCMs include greenhouse effect, volcanic and solar forcing, the more modern ones also have an ENSO like phenomenon.

    However, GCMs can't include "unknown unknowns", so your question is rhetorical as I suspect there is no answer that would satisfy you.

    Note also that we haven't said there are no unknowns, just that there is little reason to suggest they exist.
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  21. eon... It seems to me, again, that you're thinking the point of the video is to validate that warming is man-made. It's not. The video merely validates that the past 16 years of warming are consistent with the prior 16 years when you remove ENSO and volcanoes.

    Validation of the human contribution to warming comes from the overwhelming body of scientific research.

    This video is a direct response to all the places in the news media where "skeptics" are saying that there's been no warming over the past 16 years. This video neatly puts that myth to rest.
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  22. @eon - I just checked the video script and the narration at 01:20 states the following:
    What's left is the human contribution to climate change plus some wiggles due to weather.

    This is different from what you assert at #69 (as well as in some other comments) "and then bundled the remainder all as "caused by humans"."
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  23. @BaerbelW
    By comment #69 i was more responding to comments rather than the video. I did clarify further beyond an opening statement.... read "noise" and "not significant" in my comments as "some wiggles due to weather". I don't think anyone is bothered about the wiggles/weather - it is more the longer trend that is of relevance.

    I get the point of the video. I don't have a problem with the point of the video. I have a problem with the content of it -> specifically its methodology of working out the "human contributions". I have no issue with the point of the video. The videos point shouldn't have any bearing of if its calculation is correct or not.

    At least 1/3 people tried to respond to a simple question! I take it that is a "I don't know" (fair enough). Yes, it can't be measured.... but that wasn't really the question. The question is what would you expect to see.

    It wasn't a rhetoric question. The purpose of the question is to see if people really believe that the method outlined in the video, to the extent that they believe it would work for ALL time periods. If yes, then that gives "skeptics" an opportunity to prove them wrong (which is probably why people never answer yes/no questions with a straight yes or a no!)
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  24. eon... Once you remove those primary variables, what I usually get from skeptics is "we're just recovering from the LIA" or "this is just natural variability." Neither of which offers any actual mechanism for the trend.
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  25. Sorry - i should of added:
    If "yes", then that gives "skeptics" an opportunity to prove them wrong (which is probably why people never answer yes/no questions with a straight yes or a no!)
    If "no", then what's the point of the video? You can crunch some numbers for the last 30 years in one way, but the same crunch method isn't applicable for other time periods, then that doesn't sound very scientific.
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  26. eon... Perhaps there should be an addendum video that also removes forcing from man-made greenhouse gases from the trend.
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  27. In response to eon here: "Since no human contributions, no unknown contributions and all the significant factors have been subtracted/added, then by your arguments, we would see a flat graph (+some noise) ? "

    You would likely have a fairly flat graph, but with longer term variations. Here is the past 2000 years with solar and volcanoes. The MWP and LIA in this graph are attributable to both solar and volcanoes. So, I think without those you'd end up with a fairly flat graph with noise.

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  28. eon,

    If "no", then what's the point of the video? You can crunch some numbers for the last 30 years in one way, but the same crunch method isn't applicable for other time periods, then that doesn't sound very scientific.

    Over the longer term the answer is "yes and no" because you've ignored known factors that are omitted in the video because they are known to not be factors now but have been in the past.

    The forcing associated with Milankovitch cycles is an obvious one — it has been decreasing for thousands of years, leading to slow, long-term cooling, but the change is too small to be a factor at the timescale of the video, and since it's more related to the distribution of insolation rather than the total insolation, it might not have been picked up as "solar activity".

    An asteroid impact would also have an effect.

    Long-term changes to albedo due to encroaching and retreating ice sheets or desertification are also omitted but important in the past.

    The reason I say "yes and no" is because the "same crunch method" would work for those other factors if they were a factor. If you want to use the same method to account for changes since the last glacial maximum, then simply add terms for the additional factors that come into play.

    There's nothing wrong with omitting knowns that we know aren't relevant to the period in question, however.

    If you really want to show the video is wrong, then rather than complain about unknown unknowns not being included, all you have to do is show that when adding a term for AGW that depends on net anthropogenic forcings, what is left is more than just "some wiggles due to weather". That is scientific.
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  29. eon I would have thought it obvious that the answer is "yes, you would expect to see a broadly flat trend plus some noise", as that is directly implied by the statement that there is little evidence to suggest that the "unknown unknowns" have a significant effect. However, one can't say that would apply to ALL time periods and it also leaves open the definition of "plus some noise".

    Do you agree that the video clearly demonstrates that the apparent hiatus in global mean surface temperatures is adequately explained by volcanic and solar forcing and ENSO, and that once these factors have been accounted for there is little evidence for a reduction in the rate of warming due to the enhanced greenhouse effect.

    Yes or no?
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  30. Eon: I'll try and address a couple of questions - firstly whether we can attribute what is left after removing the solar, volcanic and El Nino effects, and secondly whether the method is applicable over other time periods.

    I've made a lot of use of the 2-box+ENSO model recently, based on Rypdal 2012 (see reference in the advanced rebuttal). My aim is to make this calculation available online, but it's not ready yet. However, the results are relevant. This trivial model empirically fits temperatures to forcing with no physics except causality and a parsimony requirement - and as such is largely independent of the traditional physics based models. (You can also write it in 20-30 lines of code.) Here is what you get if you fit the GISS forcings to the temperature data:

    The forcings of course include the volcanic and solar effects, and the El Nino term has been added in as well. The explanatory power for the 130 year record is very good indeed, and the El Nino term, which is critical for the impact on the short term trend, takes on an almost identical value. The model also shows the slowdown in recent warming, for the same reason - the El Nino trend is masking recent warming.

    Unfortunately the forcing data is annual and only runs to 2010, so I couldn't use this approach for the video, but it certainly looks as though the longer term data supports a similar conclusion to that of the video. Integrating the two calculations is one of my longer term aims, and will I believe produce a more robust result.

    But we can draw some conclusions. The fact that the forcings + El Nino explain the temperature record so well means that the temperature record does not provide an intrinsic reason for introducing other factors.

    Could such factors exist? Let's invent such a factor - we'll call it 'climate elves' - and introduce it into the model. In order to be plausible the climate elves would have to operate in such a way that the model still reproduces 20th century temperatures. That eliminates a lot of potential elves (e.g. solar), but not all of them. For example, once the model is online you will be able to see that you can obtain a similar fit with lower sensitivity by reducing the aerosol term. We also can't rule out a long term ocean oscillation.

    However, this calculation does not exist in isolation. For example the physical models, the glacial cycles, and climate on deep time all have things to say on this question. Suppose we introduce aerosol elves to reduce the aerosol effect and so climate sensivity, then we have to first reconcile this with the physical models. More seriously it becomes harder to explain the glacial cycle or indeed other paleoclimate features. If we reduce sensitivity too much then we can't even explain the observed volcanic cooling events.

    Therefore while I expect climate elves exist (most likely in the form of an error in the aerosol term which could go in either direction, and maybe a long term ocean oscillation), the impact is unlikely to be very large. (And even a climate sensitivity of 2C(x2 CO2) rather than the consensus 3C doesn't buy us very long.)

    Thus, given that the consensus estimates of climate sensitivity are based on a wide range of different sources of information, and both the simple and physical models explain the 130 year record with similar sensitivities, there is significant evidence basis to support current estimates of anthropogenic forcing. The scale of the natural and anthropogenic forcings are linked through the temperature record and the response function, and thus I think the statement in the video that 'what is left is the human contribution' is a fair assessment of the current state of knowledge.
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  31. Wow! The denier zombie hordes have kept me busy linking to this post at other venues, so much so that I have now saved it in my bookmarks. Thanks for providing such a good resource.
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  32. Funny how so few of them are willing to come here and discuss it. Go figure.
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  33. Rob, I have noticed a trend where comments linking to SkS posts trigger the denier zombie hordes to reply with comments like "Skeptical Science is a religious activist site, run by spin merchants", or variations of that. To counter this, I have now taken to finishing my comments linking to SkS with this:
    Skeptical Science is an award-winning web site where scientific research is discussed in a civil manner and questions from ordinary yobs like me are answered intelligently. It is well worth a visit, if you are genuinely interested in the science behind AGW theory.

    (Cue the outraged bluster from contrarians, who will claim that a science-backed venue like Skeptical Science must really be an 'AGW religious site'. Sigh!)
    So far, this tactic has worked to prevent such follow-up zombie comments, but I wonder for how long?
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  34. Technical Question on Zhou and Tung, J. Atm, Sci. vol 70, Jan 2013 pp. 3-8. Quite on topic, just out to academic libraries.. They do a regression analysis including the AMO and find this addition strongly reduces the rate at which the temp increases due to GHG. But they have data all the way back to 1850 and try only fits that are linear with time.

    Why should one even expect the GHG contribution is linear with time, especially over this long a time period? See their Fig. 4 to see problems that arise. If driven by CO2 temp increase is linear with respect to log to base two of COs concentration ratio, not linear with time and the difference will be pronounced if you go back to 1850. In my figure in comment 47 above, I get a good fit with a c.s. of 2.035 plus or minus .074. We should have, perhaps, a discussion about the Zhou and Tung paper.
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  35. curiousd,

    An issue with their analysis, IMO, is that the AMO index used is based on the North Atlantic sea surface temperature, which is not surprisingly highly correlated with global temperature change:

    Even though the AMO index is constructed by detrending the north atlantic SST, it is very likely that the nonlinear component of global warming signal is still embedded in the index. The issue is that when you use the AMO index as a regressor, you are potentially trying to use part of global temperature to explain global temperature, which exaggerates the role of the AMO.
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  36. @curiousd/ianC Tamino discussed AMO here, and makes the point that AMO may be the effect rather than the cause.
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  37. Isn't there a paper on the "shift" in the AMO-GST relationship post 1960? You can see the emergence of the GW signal in the development of the lag between GST and AMO post 1960. Or am I hallucinating publications?
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  38. I have now done the following:

    1. Went to Zhao and Tung again. At one point they show a graph where they have regressed volcanos, solar, ENSO from temperature. I digitize this graph using online manual digitizer.
    2. I look up Law Dome and Mauna Loa CO2 and correctly plot the temp, as digitized, versus log Conc/Conc 1875 as Zhou and Tung should have done.
    3. Straight line fit yields C.S. of close to 2 degrees C per doubling CO2. (Not small C.S. Zhou and Tung get).
    4. I subtract the straight line fit from their temperatures to yield a plot of temperature versus year showing three peaks about 70 years apart. We at present appear to be on top of the last, and smallest, of the three peaks.

    Question:(a) I think in principle this result is publishable, but it is based on digitizing someone else's result. I have published considerable in - say - Phys Rev, but not climate journals. Is the fact that I used digitized data going to be a killer?
    (b) If consensus answer to (a) is "forget it" would anyone here be interested in collaborating, someone who knows how to regress volcanoes, ENSO, which I do not?
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  39. curiousd @88, I do not know whether or not the used of digitized data would be a bar to publication, but the use of just log CO2 as the only forcing probably would be. It is well known that there are a number of forcings in addition to CO2. By most analyses, the CO2 forcing has been approximately equal to the sum of all anthropogenic forcings, with negative forcings (aerosols) approximately balancing other well mixed greenhouse gases. However, the uncertainty on the aerosol forcing is large, so that balance is not guaranteed, and nor will it be exact at all times. Consequently, while the use of log CO2 is useful for teaching, it is doubtful that it is useful in a publishable result.

    One small point, the 2 degree C per doubling of CO2 calculated equates to the transient climate sensitivity rather than the equilibrium climate sensitivity. There is significant variation in the ratio of TCS to ECS in models, but the central estimate is around 0.66, suggesting an equilibrium climate sensitivity of about 3 C per doubling of CO2 from your analysis.
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  40. To add to Tom's point, a more sophisticated version of the same calculation would be to use the 2-box model with a full set of forcings. This can give you a TCR estimate directly.

    However I still don't think you would have a publishable result, for the simple reason that the result is totally dependent on the uncertainties in the forcings. You can get pretty much any answer you want. This type of calculation is useful for understanding the likely contribution of different forcings and it can provide a link between uncertainties in the forcings and uncertainty in TCR, but it cannot give us a absolute answer. It is an interesting and useful tool, but only when used within its limitations.
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  41. Tom Curtis,

    Thanks for comments!

    IMO the log CO2 is an improvement on the assumption that AGW is linear with time, especially going back to 1875. If you try to fit a logarithm with a straight line it does not work well. Is it better to assume linearity, and limit data to a really short time period, then fit that with an AMO index, or assume Log CO2 and take advantage of the longer time period and not try to fit something that depends itself on the AGW trend? (BTW the Berkeley Earth folks do use a log fit to their long term temp data).

    It is not clear to me that the short time period choice is better, and at the same time I anticipate that the paper by Zhou and Tung will become one of the main denialist staples.

    If it is o.k. I will post my two curves here and see what people think.
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  42. @curiousd As CO2 is rising approximately exponentially with time (which is I suspect responsible for the near constant airborne fraction), there isn't a great deal of difference between taking radiative forcing to be logarithmic in CO2 or taking it to be a linear function of time.

    Note also the 2 degrees C per doubling CO2 will be an estimate of transient climate sensitivity and that equilibrium climate sensitivity will be higher.
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  43. Dikran Marsupial @92, a linear function is a reasonable approximation to the rise in CO2 forcing only since about 1970. Taken since 1850, it overstates the rise in forcing significantly up to then, and significantly understates it thereafter. The following shows HadCRUT4 plotted against 0.5 times CO2 forcing, ie, a transient climate response of 1.85 C per doubling of CO2:

    For what it is worth, this crude model shows a strong correlation to global temperature rise over that period, with an r^2 of 0.754. The slope of the scatter plot of observed vs predicted temperatures is 0.72, indicating temperatures have risen faster than is predicted by this model:

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  44. imho the AMO (and PDO) indexes should be incorporated in areal predictions. it's still imho possible that they are representations of an 'ocean harmonic' with the approximate periods they suggest. is there a third hithero unnoticed ocean index that would fall in between AMO and PDO peaks making these negliglible in the whole system of global heat balance? (the missing heat problem comes to mind, though that was largely solved). i'm also curious of the possibility of such a long period oscillation but thus far haven't found any detailed temperature records for the last 1000 years that would be necessary to state there is a long period harmonic in the ocean. maybe it is just the variations in aerosols (use of unleaded lowsulfur gas f.e.) that makes the 20th century reconstruction hard. One can use log CO2 instead of linear assumption, I've seen that done somewhere (it was probably someone commenting on Tamino) but I don't remember when and did he take things mentioned by Tom and Kevin into account. Of long records, I tried once to create a volcanic record for the last 1000 years but there was a snag in the Carbon dating system and I've still not corrected that.
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  45. jyyh - Given that the AMO (definition here) is a detrended sea surface temperature of the northern Atlantic, it's hugely correlated with global temperatures. Tamino discusses that here; if you look at the difference between northern Atlantic SST and GISTEMP trends, it's not terribly useful:

    Global temperatures are really the cause, not the effect, of most of the AMO. Further evidence to this end comes from looking at lead-lag relationships (here's another Tamino post on this), where analysis shows a somewhat stronger correlation with AMO lagging temperatures by a month or two - and a negative delay is a very strong argument against causality. ENSO, by comparison, best correlates with an ENSO leading by 4-5 months, the correct causal direction.

    If you attempt to relate AMO to global temperatures, there is a tendency to actually be subtracting the signal from itself, which leads to some very unrealistic estimates of climate sensitivity.


    The PDO may have some influence on global temperatures, but quite frankly we (a) don't have a huge amount of data, and (b) the duration and strength of observed PDO changes don't scale to the rapid and large temperature changes of the last 150 years. I suspect (IMO) that the PDO is at most a minor influence.
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  46. Fantastic video! May I ask how did you do your animations? I work with time series all the time and would love to have something like this for presentations. It was awesome!
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  47. KR @95, land temperatures rise faster than sea surface temperatures under forcing. That means that GISTEMP will rise faster than SST under forcing solely on the basis that it includes large sections (30%) of land, meaning a chart of the North Atlantic SST anomaly minus Gistemp is not a useful indicator of anything much.

    Far more useful, and a far better definition of the AMO, is the North Atlantic SST anomaly minus the Global SST anomaly, as shown in the third panel of this graph:

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  48. For what it's worth I've tried AMO and PDO. In both cases the statistics reject adding them to the model. In neither case does adding them change the conclusions. There will be an update in the next month or so including this and other FAQs.
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  49. Tom Curtis - One problem I see in discussing the AMO is multiple definitions; ESRL's, Trenberth, etc. Each definition really requires its own analysis, something not clear when discussing the "AMO" without further qualifications.

    Kevin C - My expectations match your results. I'm looking forward to your updates.
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  50. Hi,

    I thought of the clearest way to state what I did here.

    1. Start with data that has had ENSO,solar, volcanoes removed
    2. Go all the way back to 1861, (where the linear approximation fails...note Zhao and Tung cannot go there!(their fig.4)) and plot log2( C/C1861) on horizontal axis, temp on vertical. Find good linear fit with transient C.S close to two.
    3. Subtract the linear fit from data. Now we have data with volcanoes, solar, ENSO, and expected human caused AGW all removed.

    4. Then you get,plotted against year what I call...

    Ta ta te ta te taaah

    "What's Left!"

    IMO the plot of "what's left" versus year is veerry interesting.

    Working on posting these.
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